/****************************************************************************
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 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name PX4 nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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/**
 * @file RingBuffer.h
 * @author Roman Bapst <bapstroman@gmail.com>
 * Template RingBuffer.
 */

#include <cstdio>
#include <cstring>
#include <inttypes.h>

template <typename data_type>
class RingBuffer {
public:
    explicit RingBuffer(size_t size) { allocate(size); }
    RingBuffer() { allocate(1); }
    ~RingBuffer() { delete[] _buffer; }

    // no copy, assignment, move, move assignment
    RingBuffer(const RingBuffer&) = delete;
    RingBuffer& operator=(const RingBuffer&) = delete;
    RingBuffer(RingBuffer&&) = delete;
    RingBuffer& operator=(RingBuffer&&) = delete;

    bool allocate(uint8_t size)
    {
        if (valid() && (size == _size)) {
            // no change
            return true;
        }

        if (size == 0) {
            return false;
        }

        if (_buffer != nullptr) {
            delete[] _buffer;
        }

        _buffer = new data_type[size] {};

        if (_buffer == nullptr) {
            return false;
        }

        _size = size;

        _head = 0;
        _tail = 0;

        _first_write = true;

        return true;
    }

    bool valid() const { return (_buffer != nullptr) && (_size > 0); }

    void push(const data_type& sample)
    {
        uint8_t head_new = _head;

        if (!_first_write) {
            head_new = (_head + 1) % _size;
        }

        _buffer[head_new] = sample;
        _head = head_new;

        // move tail if we overwrite it
        if (_head == _tail && !_first_write) {
            _tail = (_tail + 1) % _size;

        } else {
            _first_write = false;
        }
    }

    uint8_t get_length() const { return _size; }

    data_type& operator[](const uint8_t index) { return _buffer[index]; }

    const data_type& get_newest() const { return _buffer[_head]; }
    const data_type& get_oldest() const { return _buffer[_tail]; }

    uint8_t get_oldest_index() const { return _tail; }

    bool pop_first_older_than(const uint64_t& timestamp, data_type* sample)
    {
        // start looking from newest observation data
        for (uint8_t i = 0; i < _size; i++) {
            int index = (_head - i);
            index = index < 0 ? _size + index : index;

            if (timestamp >= _buffer[index].time_us && timestamp < _buffer[index].time_us + (uint64_t)1e5) {
                *sample = _buffer[index];

                // Now we can set the tail to the item which
                // comes after the one we removed since we don't
                // want to have any older data in the buffer
                if (index == _head) {
                    _tail = _head;
                    _first_write = true;

                } else {
                    _tail = (index + 1) % _size;
                }

                _buffer[index].time_us = 0;

                return true;
            }

            if (index == _tail) {
                // we have reached the tail and haven't got a
                // match
                return false;
            }
        }

        return false;
    }

    int get_total_size() const { return sizeof(*this) + sizeof(data_type) * _size; }

private:
    data_type* _buffer { nullptr };

    uint8_t _head { 0 };
    uint8_t _tail { 0 };
    uint8_t _size { 0 };

    bool _first_write { true };
};
